A wooden board used in woodworking projects is typically a rectangular solid defining a pair of edge surfaces, a pair of face surfaces, and a pair of end surfaces. Ideally, the edge surfaces, face surfaces, and end surfaces of wooden boards used in woodworking projects are all completely flat, smooth, and parallel to each other.
However, the surface characteristics of raw boards used in woodworking typically vary based on numerous factors such as the type of wood, the growing conditions of the tree from which the board was obtained, the process of milling the board from the log, and changes in environment that affect the moisture content of the board after the milling process.
Accordingly, if the face surfaces of a raw board are not planar (e.g., cupped or bowed), the face surfaces are also milled such that they are substantially planar. In addition, before a typical raw board can be used in a woodworking product, the edge and end surfaces of the raw board are typically milled such that they are squared relative to the face surfaces thereof and smoothed for gluing and/or finishing.
The process of milling of a raw board to obtain a squared board thus typically involves milling of the face surfaces such that the face surfaces are substantially flat and parallel to each other and then milling of the edge surfaces such that they are smooth and perpendicular to the face surfaces.
Using modern woodworking machinery, the process off milling a raw board to obtain a squared board typically comprises the step of milling a first face surface flat using a jointer or planar, milling a second face surface flat and parallel to the first face surface using a planar, and milling the side edges smooth and square using the jointer. The end edges are typically cut to length using a cross-cut saw of some type (radial arm saw, table saw).
The present invention relates to jointers used during the process of milling a raw board to obtain a squared board. Jointers typically comprise a base supporting a blade assembly, an infeed table defining an infeed surface, and an outfeed table defining an outfeed surface. The infeed surface is substantially parallel to but not coplanar with the outfeed surface. The infeed table and outfeed table are supported by the base such that a cutting gap is defined between the infeed surface and outfeed surface. The base supports the blade assembly within the cutting gap. Typically, a jointer further comprises a fence that extends perpendicular to the infeed surface and the outfeed surface.
In use, a working surface on a board to be milled (“the workpiece”) is placed on the infeed surface. The workpiece is then moved across the cutting gap such that the blade assembly removes a portion of the workpiece defining working surface. As the workpiece moves across the cutting gap, the workpiece is supported by the outfeed surface. The workpiece may be held against the fence as board is moved across the cutting gap.
One important factor in milling a workpiece using a jointer is the depth of the cut being made. The depth of cut is determined by a distance between an infeed plane defined by the infeed surface and a reference plane defined by the blade assembly. The reference plane is a plane that is parallel to the infeed plane and which is tangential to the uppermost part of a cutting cylinder defined by the cutting assembly. In general, the depth of cut should be maximized for a particular jointer and the characteristics a particular workpiece. The workpiece characteristics relevant to depth of cut include wood type, grain structure, moisture content, and dimensions of the working surface.
Most jointers therefore allow the depth of cut to be adjusted. The depth of cut is adjusted by moving the infeed table relative to the base. More specifically, the base supports a particular blade assembly such that the reference plane defined by the blade assembly is at a certain absolute location. The base supports the infeed table such that the infeed plane is parallel to the reference plane and the infeed plane may be moved up or down relative to the reference plane.
For a variety of reasons, however, the infeed table is not supported for simple up and down movement relative to the base. The term “simple movement” as used herein refers to the movement of the infeed table along a straight line path that is parallel to a vertical reference line that extends through the rotational axis of the cutter assembly. The terms “vertical” and “horizontal” as used herein are relative to the jointer, with the infeed plane and outfeed plane both being horizontal during normal use.
One problem with simple movement of the infeed table arises from the fact that a proximal edge of the infeed table defines a portion of the cutting gap. Simple movement of the infeed table causes the proximal edge to move laterally away from the blade assembly as the infeed table moves up relative to the base, thereby increasing the dimensions of the cutting gap. If the cutting gap becomes too large, the workpiece may not be milled properly to obtain a squared board. The proximal edge of the infeed table should thus be arranged as close as possible to the cutting assembly during milling to minimize the dimensions of the cutting gap.
The infeed table is thus typically supported for complex movement relative to the base. The term “complex movement” as used herein means that the infeed table moves such that the proximal edge of the infeed table moves along a path that is not parallel to the vertical reference line.
In a first type of jointers that will be referred to herein as sliding dovetail jointers, complex movement is obtained by forming complimentary angled support surfaces on the infeed table and the base. The support surfaces are angled with respect to the vertical reference line such that the proximal edge of the infeed table moves along a linear path towards and away from the vertical reference line as the infeed table moves relative to the base.
In a second type of jointers commonly referred to as parallelogram table jointers, the infeed table is supported by two arms that are pivotably connected to the base and to the infeed table. The arms allow the proximal edge of the infeed table to be moved along a non-linear (e.g., arcuate) path. The path of the infeed table proximal edge causes the proximal edge of the infeed table to move towards and away from the vertical reference line as the infeed table moves relative to the base.
In any system that yields complex movement as defined herein, the determination of depth of cut can be problematic. Typically, depth of cut is measured by a scale system comprising a scale formed on the base and a pointer connected to the infeed table. The scale comprises a series of lines, and the distance between the lines generally corresponds to increments of depth of cut. However, because of the small distances being measured, the lines must be so small that the relationship between the pointer and the lines on the scale can be difficult to see. In addition, such scale systems are inherently inaccurate below an incremental distance of approximately 1/32″.
In addition, the need often arises to replace one blade assembly with another blade assembly. Different blade assemblies defined cutting cylinders having different diameters. Accordingly, the reference plane may be at different vertical levels relative to the base. Accordingly, conventional scale systems for measuring depth of cut in which the scale is attached to the base cannot easily be recalibrated for different reference planes established by different blade assemblies.
It should be noted that the outfeed table of a conventional jointer is typically adjustable in substantially the same manner as an infeed table. The use of an adjustable outfeed table allows the position of the outfeed table to be set to accommodate blade assemblies defining different reference planes. Typically, the outfeed table is adjusted such that the outfeed plane is substantially coplanar with the reference plane as defined by a particular blade assembly.
The need thus exists for accurate and reliable systems and methods for determining depth of cut for jointers.